The Large Data set Flashcards
Daily Maximum Temperature
Values for the daily maximum temperature are given in Degrees Celsius and to one decimal place.
A negative value indicates a reading below 0 o C.
If a reading is not available, it is listed as ‘n/a’.
Daily Total Rainfall
All the totals given are in millimetres (mm).
If the total amount of rainfall collected is less than 0.05 mm, it is referred to as a trace of rain. These values are indicated by ‘tr’ in the data set. In calculations we use 0 for these values.
If a reading is not available, it is listed as ‘n/a’.
Daily Total Sunshine
Values for this are given in hours and to one decimal place.
For example, an entry of ‘4.4 hrs’ indicates that there were 4.4 hours of sunshine in that location on that particular day.
If a reading is not available, it is listed as ‘n/a’.
Daily Max Relative Humidity
Relative humidity is a measure of how close the air is to being saturated with water vapour.
Values for this are recorded as percentages (%).
Relative humidities above 95% are associated with mist and fog.
If a reading is not available, it is listed as ‘n/a’.
Daily Mean Windspeed
The daily mean windspeed is given in knots.
1 knot is 1.15 mph.
If a reading is not available, it is listed as ‘n/a’.
The windspeeds are also categorised according to the Beaufort scale.
Light -> Moderate -> Fresh -> Strong
This is an empirical and discrete scale. You can read a little about the Beaufort scale online.
Daily Max Gust
The maximum gust speed is the maximum instantaneous speed that occurred over a 24 hour period. It is calculated as an average over a 24 hour period. If a reading is not available, it is listed as ‘n/a’.
Daily Mean Wind Direction
Two data processes are used to obtain this. The mean direction of the wind is calculated each hour. The value for the daily mean wind direction is then recorded in the Large Data Set as the most frequently recorded (i.e. modal) wind direction of these hourly data captures.
The value is given in degrees relative to the true north.
The corresponding compass (cardinal) direction is also given.
Daily Max Gust Direction
This is the direction the wind was blowing in the hour the corresponding daily maximum gust occurred.
Values are given in degrees relative to the true north. The corresponding compass (cardinal) direction is also given.
Cloud Cover
This is a discrete variable in the data set.
It is measurement of the fraction of the celestial dome covered by cloud.
It is measured in eighths.
The technical unit used in this case is called oktas.
0 oktas indicates a completely clear sky, while 8 oktas indicates complete overcast.
Visibility
Visibility is measured horizontally (how far you can see horizontally). Readings are given in decametres (0.1 Meters)
A dash indicates unavailable data.
Pressure
This is recorded in hectopascals (hPa).
The previous unit for measuring pressure was the millibar (mb).
1 bar is 1000 millibars and 1 millibar = 1 hectopascal.
